floor

Description

floor
( float$value
) : float

Returns the next lowest integer value (as float) by rounding down
value if necessary.

Parameters

value

The numeric value to round

Return Values

value rounded to the next lowest integer.
The return value of floor() is still of type
float because the value range of float is
usually bigger than that of integer.
This function returns FALSE in case of an error (e.g. passing an array).

I believe this behavior of the floor function was intended. Note that it says "the next lowest integer". -1 is "higher" than -1.6. As in, -1 is logically greater than -1.6. To go lower the floor function would go to -2 which is logically less than -1.6.

Floor isn't trying to give you the number closest to zero, it's giving you the lowest bounding integer of a float.

A correction to the funcion floor_dec from the user "php is the best".If the number is 0.05999 it returns 0.59 because the zero at left position is deleted.I just added a '1' and after the floor or ceil call remove with a substr.Hope it helps.

mathematical functions lack a floating point version of the modulo operation, which returns the difference between the floor() of the argument and the argument itself:

<?php
function fmod($value) {
return $value - floor($value);
}
?>

Very useful with trigonometric functions to reduce the angle argument to a circle that includes angle 0.

Useful also to reduce an arbitrarily large floating point value into an entropy source, by first transforming this value into a pair using logarithm functions with distinct bases (add 1 if the function can return 0, to avoid floating point errors with logarithms!):

Floats have a mind of their own, and what may look like an integer stored in a float isn't.

Here's a baffling example of how floor can be tripped up by this:

<?php
$price = 79.99;

print $price."\r\n"; // correct result, 79.99 shown

$price = $price * 100;

print $price."\r\n"; // correct result, 7999 shown

print floor($price); // 7998 shown! what's going on?
?>

The thing to remember here is that the way a float stores a value makes it very easy for these kind of things to happen. When the 79.99 was multiplied by 100, the actual value stored in the float was probably something like 7998.9999999999999999999999999999999999, PHP would print out 7999 when the value is displayed but floor would therefore round this down to 7998.

THe moral of this story - never use float for anything that needs to be accurate! If you're doing prices for products or a shopping cart, then always use an integer and store prices as a number of pence, you'll thank me for this later :)

For calculating the number of days, hours, minutes and seconds to an event.

<?php
$then = date(mktime(8,0,0,6,25,2004)); //remember that mktime is hour,min,sec,month,day,year
$now = date("U"); // "U" is the number of seconds since the epoch, equivilant to using "YmdHis"

$time = $then - $now; //gets the number of seconds between now and the event
$days = floor($time/86400); //rounds down to the whole number, in this case # of days
echo $days." Days";
$time = $time - ($days*86400); //leaves you with the amount of time ramaining after subtracting the days
$hours = floor($time/3600); //rounds down to the whole number, in this case # of hours
echo $hours." Hours";
$time = $time - ($hours*3600); //leaves you with the amount of time ramaining after subtracting the hours
$min = floor($time/60); //rounds down to the whole number, in this case # of minutes
echo $min." Minutes";
$sec = $time - ($min*60); //leaves you with the amount of time ramaining after subtracting the minutes which is equivilant to the remainins seconds
echo $sec." Seconds";
?>

You can simply make a floor with decimals function by using the round() function and subtract 0.05 to the value if the value must have 1 decimal accuracy, or 0.005 for 2 decimals accuracy, or 0.0005 for 3 decimals etc.

This works because, first, the length is multiplied by 100, which moves the decimal point to the right two places, giving us the value of 512.34. Next .5 is added to the length, which gives us a value of 512.84. Then the floor function truncates the value, leaving us with 512. Lastly, to compensate for multiplying by 100 earlier, now we must divide by 100, or in this case, multiply by .01. This moves the decimal point back 2 places to it's original place and gives us the rounded value of 5.12.

We can also round to other values, such as the thousandths, by adjusting the code as follows: